Appliances such as refrigerators and dishwashers have a door providing access to an internal chamber or compartment within the appliance. Refrigerator door construction typically comprises a front or external panel including edges, a rear or interior panel, an upper door cap and a lower door cap, and internal foam insulation installed between the front and rear panels. Appliance doors traditionally have a convex front panel, the convex curve of the door front panel noticeable in a horizontal plane through the door. However, modern appliance design has introduced appliances with doors comprising a flat front panel. Such appliances are typically premium products designed for the higher end of the market and may feature flat doors with an unpainted bright stainless steel finish, or flat doors with a clear lacquer or coating that provides a bright or reflective stainless steel finish.
Obtaining an acceptably flat door finish can be difficult. Even a slight depression or shape irregularity in a bright or reflective flat front panel can be noticeable to the eye. Such shape defects or irregularities are extremely undesirable.
Shape defects can be introduced by shrinkage of the internal insulating foam during manufacture or at some time after manufacture. During the foaming process during the door manufacture, the foam bonds to an inside surface of the door front panel. Shrinkage of the foam during cooling may occur. Also, foam shrinkage can occur due to other causes over time, for example over a period of months post manufacture. As the foam is bonded to the door panel, the foam shrinkage can pull the front panel of the door inwards. Irregularities in the amount of shrinkage can cause localized shape defects which become apparent in the flat or bright or highly reflective surface of the door. The same shape defects may be present in a door with a duller finish. However in less reflective doors such as a door with a painted or embossed finish, shape defects are less visible or apparent to a user. Also, a door with a curved front panel may also include shape defects caused by foam shrinkage, but the added panel stiffness achieved by the curvature of the front panel helps to resist the foam shrinkage resulting in smaller and less visible shape defects.
A number of solutions to overcome shape defects caused by foam shrinkage have been proposed. JP61-141690 discloses a refrigerator door with an intermediate member between the internal foam and the door front panel. The intermediate material is not bonded to the front panel so that foam shrinkage does not pull the front panel inwards.
EP1505359 suggests the door of JP61-141690 results in a bad touch due to a clearance between the front panel and the foam caused by the foam shrinkage. EP1505359 discloses a resin foam intermediate layer in between the internal foam and the door outer panel. Shrinkage of the insulating foam is absorbed by expansion of the resin foam so that deformation of the outer panel is prevented.
Another method for dealing with shape defects in flat doors is to select a dull or less bright or less reflective surface finish for the door to hide or obscure the effect of shape defects.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.
It is an object of the present invention to provide an improved appliance door, or to at least provide the industry with a useful choice for an appliance door construction.